In reply to pebbles:
> (In reply to ChrisJD) 8. apparently I'm crap with blues. good test!
Tritanomalous perhaps?
The test is an electronic version of one of the detailed colour vision tests used by opticians (none actually use it, it takes too long, but in specialist hospital clinics it might be used). You can analyse the results to show which of the cones in the retina (of the 3 types which respond most to red, green and blue light - kind of) are absent, dodgy, or just 'calibrated' a bit differently to colour-normal people's. It certainly is a good test, but there's a slightly better one where you have to try to match two patches of colour by turning dials.
Shrimps would do very well on this test, they have loads of different cone types and so presumably perceive a far greater rainbow of colours than us trichromats (animals with 3 cones). I would love to know what the world looked like to them...